Vascular Endothelial Growth Factor Polymorphism rs699947 Is Associated with Neurostructural Phenotypes in Youth with Bipolar Disorder.

Background: Vascular endothelial growth factor (VEGF) may be relevant to bipolar disorder (BD) and brain structure. We evaluated VEGF rs699947 single-nucleotide polymorphism in relation to structural neuroimaging phenotypes in youth BD. Methods: We collected 3 T anatomical magnetic resonance images from 154 youth (79 BD and 75 healthy control [HC]) genotyped for VEGF rs699947. The participants were age (BD = 17.28 ± 1.40 and HC = 17.01 ± 1.83, t = -1.02, p = 0.31) and sex (BD = 63.3% females and HC = 52.0% females, χ2 = 2.01, p = 0.16) matched. Cortical thickness, surface area (SA), and volume were examined by region-of-interest (ROI) and vertex-wise analyses using general linear models (GLMs). ROI investigations selected for the prefrontal cortex (PFC), amygdala, and hippocampus. Vertex-wise analyses controlled for age, sex, and intracranial volume. Results: ROI results found lower PFC SA (p = 0.003, ηp2 = 0.06) and volume (p = 0.04, ηp2 = 0.03) in BD and a main effect of rs699947 on hippocampal volume (p = 0.03, ηp2 = 0.05). The latter two findings did not survive multiple comparisons. Vertex-wise analyses found rs699947 main effects on left postcentral gyrus volume (p < 0.001), right rostral anterior cingulate SA (p = 0.004), and right superior temporal gyrus thickness (p = 0.004). There were significant diagnosis-by-genotype interactions in the left superior temporal, left caudal middle frontal, left superior frontal, right fusiform, and right lingual gyri, and the left insular cortex. Posthoc analyses revealed the AA allele was associated with larger brain structures among HC, but smaller brain structures in BD for most clusters. Conclusions: Overall, we found preliminary evidence of divergent associations between BD and HC youth in terms of neurostructural correlates of VEGF rs699947 encompassing highly relevant frontotemporal regions.

Hydrogel assisted photoreceptor delivery inhibits material transfer.

Cell therapy holds tremendous promise for vision restoration; yet donor cell survival and integration continue to limit efficacy of these strategies. Transplanted photoreceptors, which mediate light sensitivity in the retina, transfer cytoplasmic components to host photoreceptors instead of integrating into the tissue. Donor cell material transfer could, therefore, function as a protein augmentation strategy to restore photoreceptor function. Biomaterials, such as hyaluronan-based hydrogels, can support donor cell survival but have not been evaluated for effects on material transfer. With increased survival, we hypothesized that we would achieve greater material transfer; however, the opposite occurred. Photoreceptors delivered to the subretinal space in mice in a hyaluronan and methylcellulose (HAMC) hydrogel showed reduced material transfer. We examined mitochondria transfer in vitro and cytosolic protein transfer in vivo and demonstrate that HAMC significantly reduced transfer in both contexts, which we ascribe to reduced cell-cell contact. Nanotube-like donor cell protrusions were significantly reduced in the hydrogel-transplanted photoreceptors compared to the saline control group, which suggests that HAMC limits the contact required to the host retina for transfer. Thus, HAMC can be used to manipulate the behaviour of transplanted donor cells in cell therapy strategies.

Photoreceptor nanotubes mediate the in vivo exchange of intracellular material.

Emerging evidence suggests that intracellular molecules and organelles transfer between cells during embryonic development, tissue homeostasis and disease. We and others recently showed that transplanted and host photoreceptors engage in bidirectional transfer of intracellular material in the recipient retina, a process termed material transfer (MT). We used cell transplantation, advanced tissue imaging approaches, genetic and pharmacologic interventions and primary cell culture to characterize and elucidate the mechanism of MT. We show that MT correlates with donor cell persistence and the accumulation of donor-derived proteins, mitochondria and transcripts in acceptor cells in vivo. MT requires cell contact in vitro and is associated with the formation of stable microtubule-containing protrusions, termed photoreceptor nanotubes (Ph NTs), that connect donor and host cells in vivo and in vitro. Ph NTs mediate GFP transfer between connected cells in vitro. Furthermore, interfering with Ph NT outgrowth by targeting Rho GTPase-dependent actin remodelling inhibits MT in vivo. Collectively, our observations provide evidence for horizontal exchange of intracellular material via nanotube-like connections between neurons in vivo.

InVision: An optimized tissue clearing approach for three-dimensional imaging and analysis of intact rodent eyes.

The mouse eye is used to model central nervous system development, pathology, angiogenesis, tumorigenesis, and regenerative therapies. To facilitate the analysis of these processes, we developed an optimized tissue clearing and depigmentation protocol, termed InVision, that permits whole-eye fluorescent marker tissue imaging. We validated this method for the analysis of normal and degenerative retinal architecture, transgenic fluorescent reporter expression, immunostaining and three-dimensional volumetric (3DV) analysis of retinoblastoma and angiogenesis. We also used this method to characterize material transfer (MT), a recently described phenomenon of horizontal protein exchange that occurs between transplanted and recipient photoreceptors. 3D spatial distribution analysis of MT in transplanted retinas suggests that MT of cytoplasmic GFP between photoreceptors is mediated by short-range, proximity-dependent cellular interactions. The InVision protocol will allow investigators working across multiple cell biological disciplines to generate novel insights into the local cellular networks involved in cell biological processes in the eye.